Denafrips DACs might not actually be NOS?

[The Computer Audiophile]

I'll ask Vinshine Audio.

[The Computer Audiophile]

Perhaps @Miska has measured one of these?

[The Computer Audiophile]

Hi Guys, I heard back from Alvin, who spoke with Denafrips. He says, according to Denafrips, the NOS is indeed non-oversampling. He couldn't provide more information because Denafrips doesn't want to reveal anything proprietary with respect to how its DACs operate. 

 

I'm not sure where this leaves us, but it's all I have right now. 

[The Computer Audiophile]

3 minutes ago, GoldenOne said:

I guess maybe they could call it 'non oversampling' on a technicality in this situation given as the FPGA is just making things move in a linear fashion to the next sample.
Technically not adding extra PCM samples perhaps but still functionally oversampling/interpolating.

We know it's definitely not a slew rate or analog low-pass filter limit because the square wave transfer speed changes depending on sample rate.


The linear interpolation behaviour can be seen quite clearly on a 15khz sine:




For those who are unfamiliar this image shows what is happening in the denafrips impulse response vs what would happen in true NOS/Zero-Order-Hold behaviour (blue line):
 

- Sample 1 is received by the DAC, nothing happens and it holds at 0 until the next sample.
- Sample 2 is received by the DAC, it immediately moves up to the value of sample 2 and holds until the next sample
- Sample 3 is received by the DAC, it immediately moves down to the value of sample 3
- Sample 4 is received, same value as sample 3 so voltage stays where it is.
 

BUT, that isn't happening on the denafrips.
Instead, immediately after sample 1 arrives, it begins moving up toward sample 2. The only way this could happen is if additional samples had been interpolated in-between samples 1 and 2, ie: it was oversampling.
It is using a filter that introduces no ringing, but it is nonetheless still oversampling.


In reality a NOS impulse will look something more like this because most R2R dacs will have some form of analog reconstruction:

 

This is interesting. 

 

1. I wish we had more information from Denafrips. 

2. I wonder what the pros and cons are of doing it the way Denafrips appears to be doing it.

3. If it's not a traditional NOS design, I wonder why and if this is better or worse than a traditional NOS design. 

 

All interesting stuff!

 

[The Computer Audiophile]

2 minutes ago, GoldenOne said:

1) Yep definitely. I understand they won't want to disclose exactly how their DACs are working. Given they are indeed exceeding the accuracy of their resistors it shows that certainly some kind of compensation is both at play and working and they wouldn't want to spill their secret sauce, but it would be good to get this cleared up given as it's one of the selling points of the product

2) I guess the pro would be that it might allow for more flexible correction techniques or subsample correction with the FPGA where it might not be possible with NOS?
The con being that because it is mostly randomly (but of course in a signal dependent manner given as it depends where the samples are as to where the interconnecting interpolated line moves to/from) creating additional tones lasting 1 sample duration, this COULD maybe have an effect on noise floor with musical content?
With true NOS the transition is always just going to be vertical/near-vertical and so will remain constant. But then on the denafrips interpolation it would be random according to the signal being played.
Measurements seem fine, but given as FFT relies on content being present for long durations (hence why you can use it to look below the noise floor), the effects of what denafrips is doing here might not actually be particularly visible on an FFT.

To be honest I think the best person to ask might be @Miska. What in your opinion would be the major drawbacks of using fully linear interpolation like what seems to be happening here?
And are there any particular benefits?

 

Agree, hopefully Jussi has time to add an opinion here. 

 

By the way, I like your approach to investigating this one. Curiosity is always best when we don't have all the information, rather than finger pointing and assuming something sinister. Bravo. 

[The Computer Audiophile]

I think the issue is that we are missing a bunch of information and people are just speculating. That’s only slightly interesting to most people. 

[The Computer Audiophile]

3 minutes ago, semente said:

 

And it upsets fanboys...

It certainly could. But on the other hand, if we had more information, it may make them happy because there may be something going on that's contributing to the positive results everyone is hearing. This is why I asked about pros and cons of what people believe is going on.

 

Some people always assume nefarious intentions and like to take down companies while reveling in schadenfreude. Not me. 

[The Computer Audiophile]

6 minutes ago, numlog said:

 they call it NOS, it isnt NOS, no speculation involved here. The hows and whys are nice to know, but doesnt change the fact

But the big part that's missing, is what's actually going on and why. It's clearly doing something other than OS and straight NOS and I'd love to know the details. Perhaps this gives them better performance and there really isn't a term for the approach, with NOS being closest. I have no idea.

 

The comments are from some are typical accusatory, the world is black & white style that really don't help anyone. 

[The Computer Audiophile]

I wouldn't jump to any conclusions without more information. 

[The Computer Audiophile]

28 minutes ago, idiot_savant said:

may be an honest design error, or desired, so some comment would be helpful?

 

Completely. A comment or more info would be great. It’s clearly not OS and not a traditional by the book NOS as defined. 
 

 

29 minutes ago, idiot_savant said:

lay my cards on the table and say that NOS is IMHO a flawed approach anyway

Even when using far better over sampling prior to the DAC in something like HQPlayer?

[The Computer Audiophile]

3 minutes ago, idiot_savant said:

@The Computer Audiophile good point - maybe I should have said “a NOS playback *system* is IMHO a flawed approach, and offering a NOS filter at 44.1kHz is a bad idea under most circumstances*”

* maybe you hate your tweeters, or your dog

 

*if* this unit is using a linear interpolate to generate ( say ) 768k internally, and you feed it 768k via eg HQplayer it probably is irrelevant. 

 

playing back  44.1kHz audio unfiltered is IMHO a bad idea, and I’m genuinely interested as to why people disagree. 

 

your friendly neighbourhood idiot 

I have no clue why anyone would use anything in NOS mode without using external over sampling. 
 

I send 1536 kHz to the Terminator in NOS mode, using HQPlayer filtering. 

[The Computer Audiophile]

1 hour ago, idiot_savant said:

MHO the problem here is that you have a DAC that ( as it stands ) you can set it up to be really quite poor in frequency response terms, then as you increase sample rates via eg HQPlayer it suddenly sounds much better, when it could have been perfectly fine already

But using HQP you can take this DAC way farther than any internal filtering and over sampling could do. The horsepower in any DAC is just too weak to do what HQP does. That’s why people like NOS type DACs. 

[The Computer Audiophile]

2 hours ago, idiot_savant said:

@The Computer Audiophile I actually think that @etane makes a good point here - you're talking about very heavily OS *system*, yet there are many references to "NOS". You agree (thankfully) that NOS at redbook rates is not a good idea, yet many people will say that is what NOS *is* - no processing, what's on the CD is presented "purely" ( which is, IMHO not ideal ). Does it say in the user manual or advertising that you need to buy a PC and 3rd party software to optimise it? 

 

I think we're moving steadily off-topic, but...

 

As for HQPlayer taking this DAC much farther, what do you mean? You can move it farther from the speakers? Better frequency response? Lower noise floor? Less distortion? As for horsepower, how much is enough? If you're talking about reconstruction filters, a modern FPGA will have "more than enough" to comfortably exceed any realistic requirements. For example, a Xilinx Artix7-200T, as used by e.g. the Chord MScaler according to the Xilinx datasheet can do 9.2GMAC/s sustained, a Mola Mola Tambaqui has something like 2.7GMAC/s, and because they doesn't have to run e.g. Windows, OSX or Linux, then you don't run into any of the classic problems of actually extracting performance from CPUs ( cache misses, task switches, IO ). Is there a penalty or benefit for moving higher-rate audio *into* the DAC rather than doing it internally? Is there a penalty for having a highly clocked CPU in the same location? Is the Denafrips OS implementation not ideal?

 

I'm not saying any approaches are necessarily better than other ones, and I'm certainly not talking about particular products, but as you yourself said, it's not black and white - bigger number and more processing does not guarantee better measurable performance or sound quality.

 

The job of the reconstruction filter is a holistic one - in a particular architecture, the digital OS and analogue filtering *should* be closely aligned and complement each other - there is, for example not much point in oversampling to very high rates if the analogue filtering cuts in early - you are literally just adding switching noise, and vice versa if the OS filter is gentler than the analogue filter is designed for, you can easily run into slew-rate limiting, things becoming unstable etc. Also, some companies may also choose to tweak their digital filter to compensate for deficiencies in the analogue filter ( e.g. the analogue filter is a bit droopy, so a bit of DSP can give a peak appropriately ) - this is obviously problematic if you separate the two.

 

Is an R2R NOS DAC still "pure" if you have a PC doing OS & noise shaping to help linearise it? 

 

your friendly neighbourhood idiot

@Miska is far more capable of talking about his product HQPlayer and the concepts than I am. 

[The Computer Audiophile]

35 minutes ago, idiot_savant said:

I'm not especially interested in details about implementations

That's understood. 

 

You listed tons of stuff that really shows you haven't looked much into the world of over sampling outside of DACs and I attempted to get someone involved to drop more information into this thread. Suggesting that current audio hardware is fully capable of all that's needed is a bit strange to me, but alas, if you aren't interested that's OK to.

[The Computer Audiophile]

1 hour ago, ecwl said:

I have to admit I’m very confused by this discussion.

Granted, we have no idea what Denafrips Ares is doing in it’s implementation of NOS R2R playback.

But I see lots of people getting upset over NOS R2R not being truly R2R. But I’ve mentioned in other posts before that many DSD playback is not truly DSD either. And it seems that nobody gets very upset about that and vigorously defend it as “normal”.

To clarify, almost all “true” DSD playback is actually DSD with shift register with multiple elements. So technically, you’re not hearing “the original DSD” signal because of the multiple elements with shift register. And people tell me that’s normal and that’s still true DSD.

Let’s imagine Denafrips NOS also uses a shift register system for playback with say 16 R2R DACs all shifting at 16fs for 44.1kHz so you’re getting 16 R2R DACs all playing NOS except they’re all shifted by 705.6kHz = 1.4ms. To me, that’s still NOS (albeit with a type of filtering of some sort, which you’ll always need with NOS DACs, usually with an analog filter)

So how exactly is that different than a 2.822MHz DSD with 32-element shift register playback? Are we going to have people start demanding that their DACs be 1-element DSD DACs or else, their DSD DACs aren’t pure?

 

That said, maybe my understanding of NOS R2R DACs and DSD DACS are too elementary so perhaps somebody with more insights can explain to me the difference?

 

Agree, this is similar to the point I'm trying to make. The world isn't black and white and a company isn't misleading people or wrong because it's doing something different than what a "purist" may believe should happen. 

 

More information would be great, just so people can understand what's going on (for those that are interested), but it seems that many people are only interested in something else. 

[The Computer Audiophile]

1 hour ago, idiot_savant said:

If you posit that by using more horsepower for a task in a PC you can get a measurable parameter that is better than doing it internally, that must be quantifiable?

It's all measurable. You just seem to be writing it off without knowing much about it. Take a look at the filters and modulators in HQP. They are really powerful and can be resource intensive. The FPGA hardware to run them is about $2,000 (if I remember correctly) without any markup. Nobody has put this into a DAC yet. 

[The Computer Audiophile]

1 minute ago, idiot_savant said:

All I'm doing is questioning the black and white view that throwing more horsepower at a problem is always the solution

Nobody here has said that. 

 

1 minute ago, idiot_savant said:

You're the one stating that there is no current hardware currently capable, without stating capable of what?

Here's a link to the software that many people use - https://www.signalyst.com/consumer.html

 

 

[The Computer Audiophile]

16 minutes ago, idiot_savant said:

I don't know why you think I'm some clueless buffoon

I haven't said anything of the sort. 

 

The impression I get is that you now quite a bit, but may be unwilling to exit a comfort zone or are quite skeptical of external oversampling and noise shaping etc... Thus, you haven't really looked at it much. 

 

 

[The Computer Audiophile]

4 minutes ago, etane said:

Personally, I believe whether whatever iteration of "NOS DAC" is compatible with whatever post process software such as HQPlayer is a red herring.  The question should be IS THE NOS DAC AUTHENTICALLY A NOS DAC? 

 

NOS DAC is well defined by enthusiasts by products that use NOS DACs such as the list provided by @semente:

But other people like NOS DACs with Redbook. People using Audio Note, Lampizator, Border Patrol, AMR, 47Labs, Zanden, etc. DACs.

 

And, if it differs in design, implementation, technology and, most importantly, in SOUND, then it's not classically, technically or authentic(ally) NOS.   Of course, R2R removes the possibility of using traditionally used NOS chips from TDA or AD.  So, maybe by definition NOS R2R is NOT NOS and consumer should not expect NOS R2R to sound authentically NOS.

Perhaps we need more or better terminology due to different topologies and DACs on the market. 

[The Computer Audiophile]

53 minutes ago, manueljenkin said:

I have explored a fair bit on this, and I haven't been impressed with any Hqplayer interpolator, technically or sonically (a smooth fft chart is no guarantee of optimal random signal performance which is more critical for audio). Also sinc + 44.1k doesn't sound anywhere close to as good as high res PCM or arc predict + 44.1khz (which sounds quite great as well). Now I don't want to hold this universal either. Of course there may be other systems and preferences that might make HQP work fine in other systems. But it's a vague thing to assume someone's knowledge or experience is limited just because they are not impressed by something you are impressed on.

 

Point is, it would be a short sighted view to think a LTI interpolator is end all fix for a real world signal interpolation scheme, one that also involves deviations on the analog side, and also the thought that everything needs massive computation to be accomplished. Wadia and luxman have had products with spline based interpolators. There are many dacs that use custom no pre ring apodizing filters matched to their dac analog profile. There's a few where analog and digital part play together (almost all ess dacs, and more). A gazillion tap filter is useless if the actual interpolation algorithm is not the optimal choice, it is useless if all the claimed benefits gets buried in randomness of intrinsic electrical and magnetic interactions in the analog stage.

 

I have respect for everyone trying every approach, but unfortunately, people tend to think they've got the grasp hold of absolutes just by looking at synthetic charts. Real world systems and signals are too profound and complex. I have seen what's possible with efficient customized and optimal interpolation filter design and wouldn't ever think about a sinc filter for high fidelity audio again.

I always look at it as, the more you know, the more you know you don’t know. 

[The Computer Audiophile]

6 hours ago, sdolezalek said:

You know, if we strip away all the clutter around HQPlayer, upsampling, filtering, etc.  this boils down to a good objectivitist subjectivist test:

a) a lot of people really like the sound of the Denafrips DACs, particularly the Terminator models; does this new (incomplete) technical information make you like the sound less?

b) for those who only want the purest in numbers, are you now disqualifying yourself from liking a Denafrips until the question of how it sounds the way it does is cleared up?

 

Advanced test:

c) Chris, having just written the Terminator review, does this information make you any less enthusiastic about your review of this DAC?

Agree. 
 

This whole discussion changes nothing about my impression of the DAC. It does make me more interested in how the DAC works and I wonder if we need more ways to classify DACs for those interested in classification. 

[The Computer Audiophile]

4 hours ago, idiot_savant said:

I didn’t actually realise you had reviewed this pair, and perhaps were taking my comments as a negative against you, which I really wasn’t

Hi IS, I never take any of this personally and I assumed you had no idea I’d just reviewed the DAC. My main concern with this discussion is facts and not jumping to conclusions. 
 

I’m concerned that consumers will read statements claiming this DAC isn’t NOS and assume something nefarious is afoot. There may be excellent reasons for why Denafrips does what it does, but we just don’t know. 
 

There is a movement to take down companies by using measurements as weapons with carefully crafted statements that don’t tell the whole truth. It shoots first and asks questions later. Many mistakes are made that need correction. The losers in all of this are consumers and companies who are slandered due to folks that don’t care about getting all the facts first, don’t care about getting things 100% right, but really care about the appearance of saving people and finding problems with product designs. 
 

I’m not saying any of this is going on here, and in fact I know GoldenSound would never do such a thing. I just want to make sure the thread doesn’t accidentally drift in that direction. 

[The Computer Audiophile]

43 minutes ago, idiot_savant said:

The thing I'm finding interesting is that people are so set against a certain design - so e.g. R2R NOS people who hate D/S, but then use a PC to increase sample rate and reduce word depth to improve linearity... which is exactly what most D/S designs do...

This hobby, like most, is full of people along a continuum. If you look hard enough you’ll find people doing just about everything, even when it seems quite nonsensical. 
 

I don’t think it makes much sense to be against a design in general. It’s all about implementation and the end result. That’s just me though. 

[The Computer Audiophile]

37 minutes ago, numlog said:

@The Computer AudiophileSorry but you keep repeating as if this could be some NOS/OS grey area. It is clearly OS, as confirmed by others based on all the evidence presented. 

If you think it isn't or have doubts, feel free to explain. 

 

A NOS DAC always plays exactly what you feed it without digital processing, be that hi res, red book or OS data at any sample rate, this is how every early Multibit dac chip operated and is where the definition came from.

 A grey area would be others forms of DSP like equalisation,

OS, that is a process that increases the sample rate of the input and adds new samples, is obviously not one.

 

 

 

 

No. 
 

its NOS at 1536 kHz, which is how I use it. 
 

The world is full of gray areas. As much as you try to put everything in a black or white box, this doesn’t make it so. 
 

I don’t understand your push to be so rigid. We don’t have a category for this DAC. Can you be OK that, or must you call it OS which it clearly isn’t?

[The Computer Audiophile]

Peter, as a manufacturer of competing products to Denafrips, please be careful in what you post. Most of the time it isn’t ok to boast about your products, like you’ve done in this thread. 
 

Please stick to facts unrelated to your specific products.